An energy harvester from human vibrational kinetic energy for wearable biomedical devices

Abstract

An electromagnetic kinetic energy harvester has been a topic of considerable interest over recent decades because it is suitable for harvesting human’s kinetic energy at low frequency with the high power density. A small, wearable and portable electromagnetic energy harvester was developed and aimed at applications such as extending the operating period of bio-medical devices through constant charging of batteries. The proposed harvester consists of a snake-shape polydimethylsiloxane cantilever, a coil and anNdFeB magnet enclosed in a polymer casing. Its resonant frequency is ~6.6 Hz and the peak-to-peak output voltage is ~10 mV when tested on a shaker with an acceleration of 0.3 g. When tested at 1.5 g to mimic the acceleration when a person walks, the peak-to-peak output voltage is ~40 mVpp. An unconventional method of voltage rectification has been demonstrated using the combination of a miniature transformer and capacitors to produce unipolar pulses that can be used to trickle charge a battery. Although still not a perfect rectification, nevertheless this method has the potential to replace a diode in the standard rectifier.